1. Field of the Invention
The present invention relates to a binocular instrument (telescope and microscope) having a pair of right- and left-hand optical systems and a protective section for protection of the optical systems, where its pupil (interpupilary) distance is adjustable.
2. Related Art Statement
In general, a binocular instrument is constructed such that objectives and eyepieces are set at front and rear end portions of a pair of lens barrels in an exposed state to the external, which incurs attachment of dust and greases on the surface of the lenses if it is left as it is in non-using state (in a stored condition), so that there is a possibility of damages to the lenses when the attached dust or the like is wiped up. For this reason, lens caps have been used as lens protective members for a group of objectives and a group of eyepieces of the right- and left-hand lens barrels.
Meanwhile, since the lens cap is fitted over the barrel circumferential surface only under contact pressure, it can easily be removed therefrom by an external force or the like or can be misplaced. For preventing misplacement, there has been proposed a binocular instrument in which one end of the lens cap is connected through a string-like member to the barrel body.
However, if the lens cap is connected through a string-like member to the barrel body, the binocular instrument becomes hard to handle because the lens cap is unstable while being removed, besides its appearance is unacceptable.